On a lake here in SE Wisconsin I have started to see the local police spending time on the popular lakes and handing out littering tickets. They also got quite a few DUIs while out there. This would be probably the best solution to the problem that I’ve seen. Once word gets out that the cops are hanging out on the lake it’ll clear out pretty damn quick. Once the weekend party crowd started getting busted the lake seen marked improvement. The drawback is the local police are being taken away from other duties.